Determination of reducing sugar by Max-Muller and total sugar and sucrose in malt extract Preparation of water extract for determination of carbohydrates
Instruments, laboratory glassware, reagents: technical loss, water bath, thermometer measurements below 100 ° C, glass funnel, eyedropper, flask capacity 250 cm3, graduated cylinder capacity of 100 cm, porcelain cup, filter paper, a solution of NaOH (32 g 1 dm3) solution of Pb (NO3) 2 (340 g per 1 dm3), sodium sulfate (saturated solution), distilled water.
Progress definitions
1.2 g malt extract weighed in a porcelain cup on industrial scales to the nearest 0.01 g sample of the product taken from a calculation of sugar concentration in the filtrate 0.8 - 0.4%.
Take a sample of the test product is transferred to a volumetric flask capacity 250 cm3, cup washing several times with distilled water. The amount of water is equal to 100 cm3. The flask containing hot water bath and then make 3-4 cm3 of sodium hydroxide solution. The content of the flask and stirred 'll add 5 cm of lead nitrate . If the solution is not transparent for 5-7 minutes , add another 1-2 cm3 of both solutions. We're sure that there was no excess of alkali that promotes the oxidation of sugar. To remove excess lead to the illuminated solution , heated to 60 ° C, 'll add 3.4 cm3 of a saturated solution of sodium sulfate and left at the same temperature for 10 min in a water bath , then cooled . It formed large crystals of lead sulfate , which are easily filtered .
The resulting solution was tested for complete precipitation of excess lead, adding to bulb by the wall a few drops of sodium sulfate . In the absence Muti touch and place liquid flask topped up with distilled water to the mark , mix and contents of the flask after 1-2 min filtered through a filter. In the case of muti to the resulting solution 'll add another 5-7 cm3 of a solution of sodium sulfate . The content of the flask was stirred , allow to settle and re- checked for completeness deposition. Filtered colorless solution can be used to determine the mass fraction of sugars by chemical method.
Determination of reducing sugar by Max-Muller
Instruments, laboratory glassware, reagents: electric stove, stopwatch, with a capacity of 25 cm3 pipette, conical flask with a capacity of 150-200 cm3, Bunsen flask, measuring cylinders with a capacity of 50 and 10 cm3, burettes, glass filter, glass rods, and Fehling solution, Fehling solution II, a solution of iron ammonium alum, potassium permanganate solution, distilled water.
Progress definitions
For determination of reducing sugar by Max- Muller to analyze pour water extract prepared in a conical flask with a capacity of 150-200 cm3 consistently make 25 cm3 pipette solution Fehling I and Fehling II. The resulting mixture was heated to boiling and poured with a pipette 50 cm3 of the solution prepared for analysis . Boil exactly 2 minutes, counting the time from the first appearance of the surface bubbles. After boiling, allow the precipitate to settle copper .
A solution of the residue should be blue from excess Fehling solution . If the solution discoloured , indicating partial oxidation of sugar, the analysis should be repeated , slightly decreasing , but exactly measured volume of the filtrate analyzed . In flask add distilled water in an amount that, together with a new volume of 50 cm3. In Bunsen flask carefully decanted test solution without transferring the precipitate to the filter . The precipitate always be covered with liquid to prevent oxidation Su2O oxygen. This residual solution after draining the filter to precipitate copper oxide is added 5-10 cm3 pre- boiled (to remove oxygen ) of hot water, and after re- deposition of copper oxide the water was decanted through a filter. Operation washing, sedimentation, decantation with hot water repeated several times until the disappearance of the blue color wash water .
After washing liquid is poured from the flask , and the flask was thoroughly washed with water. Then the conical flask with sediment copper , located under a small layer of wash water , poured to dissolve the precipitate in small portions 30 cm3 solution of iron- ammonium alum . Oxidized copper oxide and iron oxide is reduced to iron. The resulting light- green liquid is poured gently on the glass stick to the same filter in earlier prepared flask. It dissolves copper oxide particles that got into the filter before.
For better dissolution of copper particles surface filter and fluid gently stirred with a glass rod . After dissolution Su2O conical flask and the filter washed well with distilled water , and the liquid from the bulb passed through a filter. The filtrate was titrated by 0.1 M solution of potassium permanganate to neznykayuchoho for 30 s light pink color.
Thus sulphate of iron (II) sulfate passes into iron (III) by the reaction :
10FеSО4+ 2KMnO4 + 8Н2SO4 = 5Fе(SО4)3 + К2SО4+ 2МnSО4 + 8Н2О
For Max- Müller method for calculating the results of the analysis is based are constant values for copper titer KMnO4 1 cm3 - 10 mg. Therefore, the volume of potassium permanganate taken for titration, multiply by 10 and get the appropriate amount of reducing sugar it .
Mass fraction reducing sugar (glucose , fructose ) is calculated as follows:
Х = 100m1V/1000Mv1
where m1 - mass of reducing sugar , found by empirical tables mg;
M - mass of the test sample of the product, g;
V - capacity volumetric flask , taken for the preparation of aqueous extract (250 cm3 );
V1 - volume of filtrate taken for determination of sugars cm3 , 1000 - conversion factor milligrams to grams.
Laboratory work 6
Determination of starch content in potatoes by Evers.
Devices laborotory glassware, reactants.
Saccharimeter, polarimetric cuvette length of 200mm, technical scales, water bath, stopwatch, thermometer, measuring flask 100sm3, a 25 cm3 burette, funnel, filter paper, 0.3 N solution of HCl, coagulants reagents (reagent Karreza I and II or 4% - solution of phosphotungstic acid or a solution of ammonium molybdate).
In a dry flask with a capacity of 100 cm3 burette 25sm3 made with 0.321 N HCl solution and added through a funnel with constant stirring sample of the test product ( potato pulp ) weighing 5 g, weighed with an accuracy of ± 0,01 g When the material is well mixed , washed funnel and upper portion of the new bulb (25 cm3 ) of the same acid. Flask with constant stirring immersed in boiling water and shaken for 3 min ( with a stopwatch ). Heat in the bath still another 12 minutes. After 15 min. after immersing the flask in a bath it removed, topped with cylinder 40sm3 cold distilled water and rapidly cooled under the tap and 20 ° C.
For the deposition of protein and lighting solution in the flask topped cylinder reagents - osadzhuvachi : the 2sm3 reagent Karreza I and II or 5sm3 4 % solution of phosphotungstic acid or 6 cm3 solution of ammonium molybdate . After 5 min. prove the contents of the flask with distilled water to the mark , shaken and filtered through a folded filter . The first portion of the filtrate (10 cm3) do not use. Transparent filtrate at a temperature of 20 ° C polarimetric fill tube length of 200 mm and the measured polarization at Saccharimeters , receive testimony polarization P1.
In parallel control experiment is carried out for an amendment to the optically active water-soluble substances that are deposited reagents - osadzhuvachamy and which are in solution (mainly carbohydrates ).
The control experiment
Weigh 10 g of potato pulp , carry it in a flask with a capacity of 100 cm3 , add 70 cm3 cylinder with water and with frequent shaking to stand for 40 min. Then wash the upper part of the flask 10 cm3 of distilled water, reagent - illuminated light, which is used mainly experiment . Add 5 ml of 10 % solution of tannin , 5 ml of lead acetate , shaken for 5 min. , Bring the contents of the flask to the mark with distilled water , mix and filter. Sampling is a pipette 50 cm3 filtrate is transferred to a volumetric flask of 100 cm3 , add 2 cm3 of 25 % solution of HCl , stand 15 minutes. in a boiling water bath , cooled to 20 ° C, polarize the tube length of 200 mm Saccharimeters . Prepared showing polarization P2.
Starch content calculated using the formula:
,
where:
Kp - mass fraction of starch, % by weight of dry matter ;
P1 value of the angle of rotation of the polarization , which is optically active substances mainly experiment , ° L;
P2 - the angle of rotation of the polarization plane , which is water soluble optically active substances (non- starch ) in the control experiment , ° L;
(P1 - P2) - the angle of rotation of the polarization plane , which is soluble starch sample , ° L;
m - mass of the product is taken for analysis, 5 g ;
L - length of polarimetric cell, 2dm ;
[α] d20 - rotating relative ability of potato starch in degrees of arc ;
W - moisture content in potatoes ,%;
0.3462 - conversion factor from degrees to degrees of arc sugar scale.
When taken for analysis navazhtsi 5g mass m and length polarimetric cuvette 2 dm formula takes the form:
where F - Evers factor, which is 1000 0,3462 / [α] A20
When calculating the mass fraction of starch using Table 1, which shows the value of specific capacity rotating [α] d20 coefficient and Evers (F) for the main types of starch.
Laboratory work 7
Determination of starch